Problem: $ { \left[\begin{array}{rrr}{-2} & {2} & {1} \\ {1} & {2} & {1}\end{array}\right]+\left[\begin{array}{rrr}{0} & {0} & {-1} \\ {0} & {4} & {3}\end{array}\right] = {?} } $
To find the sum of two matrices, add the corresponding items between each matrix. ${\left[\begin{array}{rrr}{-2}+{0} & {2}+{0} & {1}+{-1} \\ {1}+{0} & {2}+{4} & {1}+{3}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{-2} & {2} & {0} \\ {1} & {6} & {4}\end{array}\right]}$